This invention is related to a sink roll assembly, used for providing tension to a metal strip while rotating in molten metal, that includes forced film lubricated bearings and self-aligning holding arms. Generally, a sink roll assembly as used in the galvanizing industry comprises the following components: a roll to guide and provide tension to the metal strip, holding arms at each end of the roll to support it, and bearings in each arm to allow for its rotation.
Sink roll shafts submerged in molten zinc or zinc aluminum typically have a very short life not only because of the distortion and misalignment created between the components by the high metal temperatures in which they are operating, but in addition, because of the chemical reactions that occur between the hot metal, the bearings and the roll shaft materials when operating on a boundary lubrication condition or metal-to-metal contact.
I have solved some problems related to these environmental conditions. See, for example, my U.S. Pat. No. 5,549,393 issued Aug. 27, 1996, for xe2x80x9cSelf-Aligning Bearing for High Temperature Applicationsxe2x80x9d, U.S. Pat. No. 5,718,517 issued Feb. 17, 1998, for xe2x80x9cSelf-Aligning Bearing for High Temperature Applications; U.S. Pat. No. 6,261,369 issued Jul. 17, 2001, for xe2x80x9cSink Roll for Galvanizing Bathxe2x80x9d; U.S. Pat. No. 6,004,507 issued Dec. 21, 1999, for xe2x80x9cMaterial Formulation for Galvanizing Equipment Submerged in Molten Zinc and Aluminum/Zinc Meltsxe2x80x9d; and U.S. Pat. No. 6,168,757 issued Jan. 2, 2001 for xe2x80x9cMaterial Formulation for Galvanizing Equipment Submerged in Molten Aluminum and Aluminum/Zinc Meltsxe2x80x9d.
The invention disclosed in this application enhances the sink roll assembly (roll/holding arms/bearings assembly) as currently being used while submerged in zinc and zinc/aluminum applications, by providing self-alignment capability to the roll/arm interface, and a pumping device connected to the submerged trunnion or roll to deliver pressurized molten metal at the bearing interface to balance the strip tension forces and generate a forced hydrodynamic film to lubricate the bearing components. A radial clearance of about 0.001 to 0.005 inches is provided by the delivered pressurized metal to act between the stationary and rotating surfaces to eliminate the normally metal-to-metal condition of sliding bearing components.
In addition, the rotating bearing components help to xe2x80x9cdragxe2x80x9d the hydrodynamic molten metal film into the created clearance, thus reducing sliding friction, micro welding and their consequent high wear.
The hydrodynamic film also functions as a hydraulic shock absorber besides avoiding metal-to-metal contact.
Still further objects and advantages of the invention will become readily apparent to those skilled in the art to which the invention pertains upon reference to the following detailed description.